紫色土丘陵区秸秆还田的腐解特征及对土壤肥力的影响

在分析水稻、小麦、油菜秸秆的养分含量和化学组成的基础上，通过田间两年四作的定位试验，探讨了紫色丘陵区秸秆还田的腐解变化及对土壤肥力的影响。结果表明，秸秆含有丰富的养分，经腐解后给土壤提供了大量的碳、氮、磷、钾。在腐解过程中，还田后的前3个月分解快，后期分解缓慢；3种秸秆在田间的分解速率（K）：麦秸〉稻草〉油菜秸，秸秆翻埋〉秸秆面施；养分释放速度钾〉磷〉氮。测定了不同处理的土壤水分特征曲线．并将实验结果拟合为经验关系式。秸秆覆盖还田促进土壤团粒结构形成，提高了土壤水稳性团聚体含量，从而改善了土壤通透性和保水保肥性。秸秆覆盖还田还降低了土壤容重，增加了土壤总孔隙度，使土壤有机质、速效氮、磷、钾得到一定提高，从而达到培肥地力的目的。

Decomposition Characteristics of Straw Return to Soil and Its Effect on Soil Fertility in Purple Hilly Region

Based on analysis of chemical compositions of three crop straws(rice,wheat and rape),decomposition characteristics of straws and its effect on soil fertility in hilly area of Sichuan Basin was investigated through a fixed field experiment of two years.The results indicated that the soil was enriched with C,N,P,K when straw was returned to soil.The decomposition rate of straw in the first three months was faster than the later date.Decomposition rate(k) from the three straws followed the order as wheat straw > rice straw > rape straw,and straw-buried > straw-mulched.The content of nutrient releasing was characterized as K>P>N.Soil water retention curves of different treatments were derived,and the correlation coefficient of empirical equations were over 0.87.Straw mulched could improve soil granular structure,and increase the content of water-stable aggregates,so the ability of permeability,fertilizer and water conservation got improved.At the same time,the soil covered with straw was favorable to reducing soil bulk density and increasing soil porosity,soil organic matter,available N,available P and available K as well.So it realized the goal of soil fertility improvement.